I. Field
The present disclosure relates generally to communication, and more specifically to a pilot design for a wireless communication system.
II. Background
A wireless multiple-access communication system can support multiple users by sharing the available radio resources. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal FDMA (OFDMA) systems, and Single-Carrier FDMA (SC-FDMA) systems.
A wireless multiple-access system may support multiple-input multiple-output (MIMO) transmission on the forward and/or reverse link. On the reverse link (or uplink), one or more terminals may send transmissions from multiple (NT) transmit antennas at the terminal(s) to multiple (NR) receive antennas at a base station. A MIMO channel formed by the NT transmit antennas and the NR receive antennas may be decomposed into NC spatial channels, where NC≦min{NT, NR}. Improved performance (e.g., higher throughput and/or greater reliability) may be achieved by exploiting the spatial channels formed by the multiple transmit and receive antennas.
For MIMO transmission on the reverse link, the wireless channel between each terminal and the base station is normally estimated and used to recover the data transmission sent by the terminal via the wireless channel. Channel estimation is typically performed by sending pilot from each terminal and measuring the pilot at the base station. The pilot is made up of symbols that are known a priori by both the terminal and the base station. The base station can thus estimate the channel response for each terminal based on the pilot symbols received from that terminal and the known pilot symbols. Since pilot transmission represents overhead, it is desirable to minimize pilot transmission to the extent possible. However, the pilot transmission should be such that the base station can obtain a good channel estimate for each terminal.
There is therefore a need in the art for techniques to send pilot such that a good channel estimate may be derived.